In the early days of telecommunications, so few telephones existed that, when an individual received a telephone call, he or she almost knew where it was coming from before answering. As telephone systems have developed, however, it has come to be that there is scarcely a home, apartment, or condominium that does not have a telephone. Certainly, the telephone has come to be an essential item in a residence and not merely a luxury.
The situation is more acute when one considers the exigencies involved in a business scenario. Conditions now dictate that more business is done by the telephone than in face-to-face encounters. It is extremely difficult to imagine a successful business not having multiple lines available so that in-coming calls are substantially always able to get through. This is the case even in instances of very small businesses.
In the case of very large businesses, not only are there multiple stations serviced by a common PBX to make extensions available to many employees, but it is frequently the case that a common PBX covers far-flung facilities. For example, a large multi-national company might have a manufacturing facility in a particular geographic area and a stocking warehouse which, while in the same general geographic location, is at some distance from the manufacturing facility. Stations in both the manufacturing facility and the stocking warehouse, however, might be serviced by the same PBX.
In the relatively recent past, the United States has implemented an enhanced "9-1-1" emergency call system. Such systems function to identify a number initiating such an emergency call so that, if the person making the call is emotionally agitated or unable to talk for a long period of time because, for example, of a spreading fire, and does not, as a result, identify the specific station from which he is calling, the public safety answering point (PSAP) to which the call has been routed will be unable to fully respond in an appropriate manner because of the multiplicity of stations serviced by the common PBX. It might be necessary, however, for the PSAP, in some circumstances, to call back. For example, while the caller might identify the emergency as a fire emergency, it may be unclear as to whether ambulance and paramedic services need to be dispatched. Certainly, fire fighting vehicles and police would be dispatched, but to dispatch an ambulance or ambulances when there is neither injury nor any danger of injury would be an inappropriate utilization of resources. In fact, one can envision circumstances wherein someone else needing ambulance services might not have them available because of the inappropriate dispatching of an ambulance or ambulances when they are not necessary at the location to which they have been sent.
Under "9-1-1" emergency systems currently in use, an individual at the PSAP would be able to identify the PBX from which the call was initiated. As previously discussed, however, the facilities serviced by the PBX might be at far-flung locations. In fact, because of the inability to identify a particular station from which the call was initiated, the call might be routed to an incorrect PSAP. In the case of a large, dispersed-facility entity, the emergency services might be routed to the company headquarters. The emergency might actually be occurring, however, at a facility some distance from the headquarters. As will be understood, in the case of many emergencies, being timely and delivering the services would be essential and even a matter of "life and death".
If a person manning the PSAP incoming line were able to identify the calling station, or at least a station immediately proximate the calling station, the necessary service could be routed to the appropriate station or a designated control station that would be aware of the emergency. If the individual at the PSAP were able to identify a "call back" number corresponding to the call-initiating station, he or she would be able to get back to the calling station in a case when sufficient information was not originally elicited as to the type of emergency occurring. A determination could then be made as to what facilities should be dispatched.
Conventional telephone systems employ a public switched telephone network (PSTN) which is, typically, owned by the local telephone company. On the other hand, people or companies subscribing to particular telephone numbers, typically, own their own equipment. In the case of a company having multiple stations, a subscriber purchases a private branch exchange (PBX) console along with hand sets to be maintained at each station. The individual station handsets are interfaced with the PBX console, the console, in turn, being interfaced with the PSTN. Typically, this interfacing of the PBX with the PSTN occurs through a Central Office (CO).
It is frequently true that the protocol employed by the particular PBX equipment purchased by the user from a commercial manufacturer is different from the protocol of the emergency network. Harmonization of these protocols can present problems in identifying the particular station, of the many stations serviced by a PBX, initiating an emergency call. If harmonization does not properly occur, identification of the station initiating the call, or of a monitoring station responsible for the initiating station, will not occur.
A further problem that might be encountered in identifying a station initiating an emergency call is the development of a problem in a trunk interconnecting a station identification module to a switching tandem in the emergency network. Certainly, it would be undesirable if the first anyone became aware of the development of a problem was when an emergency call were initiated. It is virtually essential, therefore, that some means for monitoring the integrity of trunks be provided and that monitoring be able to be accomplished prior to the initiating of an emergency call.
It is to these problems and dictates of the prior art that the present invention is directed. It is a system which identifies a station initiating an emergency call, or a station responsible for the initiating station, which harmonizes the protocol of the PBX and that of the emergency network, and which monitors the integrity of trunks between the module and a switching tandem.